Printing

ABSTRACT

There is provided an apparatus and a method of printing a diffraction grating. In particular, the present invention relates to diffraction gratings applied to a substrate, such as a hologram.

The present invention relates to a method of printing, apparatus forprinting and to products obtained therefrom. In particular, the presentinvention relates to diffraction gratings applied to a substrate, suchas a hologram. More particularly, the present invention concernssub-microscopic, holographic or other diffraction gratings.

The use diffraction grating patterns and images which includesub-microscopic, holographic and other forms of diffraction gratings,especially on documents, credit cards and packaging for securitypurposes, has become commonplace. Nevertheless, despite such popularuse, the utilisation of patterns and images is expensive and involvesthe manufacture of a pattern or image in one operation and, in a secondseparate operation, the pattern or image is transferred adhered orlaminated to the intended substrate, document or article, examples ofwhich are; banknotes, cheques, gift vouchers, credit/debit cards,security brand protection and non-secure label systems and packagingitems.

Three-dimensional light diffracting patterns such as a hologram are theresult of interfering two beams of coherent light at a finite angle witheach other on a photosensitive medium. One beam is a reference beam andthe other interacts with the object whose image is to be recorded. Theresulting hologram is made having the image information recorded assurface variations of the holographic medium. A more rigid transfermaster plate is subsequently made to form replica holographic images.

There are many methods to originate sub-microscopic or holographicdiffraction gratings based on photoresist coated float glass plates,exposed to coherent light which have been manually or computercorrelated, in the form of a microscopic pattern of fringes. This ismanufactured by copying an original sub-microscopic or holographicdiffraction grating origination. A transfer plate holding thesub-microscopic structure is used to produce a metal master copy fromnickel. Subsequent generations of plates or shims can then be grown, byelectroforming.

U.S. Pat. No. 4,913,858, discloses one method of embossing holographicdiffraction pattern images into a plastic film or to a plastic coatingof a substrate. The substrate is supplied with a coating ofthermosensitive material having thermoplastic properties, heated tosoften the coating using a heated cylinder alone or in combination withinfra-red heaters and subsequently embossed to form a diffractiongrating. The coated surface is then metallised by depositing a coatingof metal on the diffraction grating. The diffraction pattern obtainedfrom such a method can be flawed owing to distortions in the grating dueto excessive pressure applied to the embossing roller to form thegrating or if the thermosensitive material is heated too much there willbe some adherence of the coating to the embossing roller. Clearly for aholographic diffraction grating, any distortions to the grating willadversely affect the quality of the hologram image.

U.S. Pat. No. 4,728,377 discloses laminated sheet material having asupport layer, a release coat covering the support layer, one or morelayers of thermoplastic material overlying the release coat and lesssensitive to heat than the release coat, and a layer of metal foilbonded to the surface of the thermoplastic layer. To form thediffraction grating, a die is impressed into the foil. The foil is thencovered with an adhesive, the laminated sheet inverted and pressedagainst the item to which the diffraction grating is to be attachedusing a heated pressure plate whereby only the area of the sheetmaterial under the pressure plate adheres to the item and separates fromthe support layer due to the melting of the release coat. When thesupport layer is lifted from the substrate, the foil and thermoplasticlayers fracture along the edges of the pressure plate.

U.S. Pat. No. 5,087,510 discloses holograms having a relief-patternedmetal surface electrolessly deposited on a relief-patterned polymericsubstrate.

All of these documents describe forming a layer of metal, to provide amirror-like luster, to improve the visibility of the image, into which asurface relief pattern is embossed using heated embossing members. If adiscrete metallised pattern is desired, the overall surface ismetallised followed by etching away unwanted metal using a suitableetchant such as an acid. Subsequently, in a separate operation thehologram is adhered or laminated to the intended document or article.

The methods described hereinabove require a significant amount of metaldeposition to provide the luster effect, and, owing to the metal layerdeposited, the image can only be viewed from the non-metallised surfaceof the substrate.

U.S. Pat. No. 5,549,774 discloses depositing metallic ink onto atransparent or translucent filmic sheet which has an embossed pattern,formed by pressing the sheet in contact with a heated nickel embossingshim at high pressure, on one surface and subsequently, in a separateoperation, bonding a backing sheet having visual information to theembossed sheet.

As described above the application of high pressure and heat canadversely affect the integrity of the diffraction grating.

The separate operation of bonding a backing sheet, i.e. the substrate towhich the hologram is to be applied, to the embossed filmic sheetreduces the speed of manufacture and can create further difficulties asthe embossed filmic sheet and backing sheet must be carefully aligned soas to prevent incorrect positioning of the embossed material.

Furthermore, the application of high pressure and heat to emboss afilmic sheet, as described in U.S. Pat. No. 5,549,774, significantlyreduces the speed of manufacture. Manufacturers have long sought toovercome the problems associated with the prior art with little or nosuccess.

Advantageously, the present invention overcomes or alleviates one ormore of the problems associated with the prior art.

In accordance with a first aspect of the present invention there isprovided a method for forming a security product comprising the stepsof:

-   -   a) providing a sheet of base material, said sheet having an        upper and lower surface and being a component of the security        product;    -   b) forming a diffraction grating on at least a portion of the        upper surface of the base material; and    -   c) depositing a metallic ink on at least a portion of the        diffraction grating;

Advantageously, the present invention provides a method of manufactureto transfer and metallise a sub-microscopic or holographic diffractiongrating directly onto the surface of a substrate and to do so with highproductivity and low cost.

In accordance with a further aspect of the present invention, there isprovided a method for forming a security product comprising the stepsof:

-   -   a) providing a sheet of base material, said sheet having an        upper and lower surface;    -   b) depositing a metallic ink on at least a portion of the        diffraction grating; and    -   c) forming a diffraction grating on at least a portion of the        metallic ink.

In accordance with a further aspect of the present invention, there isprovided a method for forming a holographic diffraction grating on asubstrate comprising the steps of:

-   -   a) applying a curable compound to at least a portion of the        substrate;    -   b) contacting at least a portion of the curable compound with        diffraction grating forming means;    -   c) curing the curable compound and    -   d) depositing a metallic ink on at least a portion of the cured        compound.

In accordance with a further aspect of the present invention, there isprovided an in-line method of printing on a substrate using aconventional printing press apparatus together with means for forming adiffraction grating, comprising the steps of:

-   -   a) forming a diffraction grating on a discrete portion of the        substrate; and    -   b) depositing a metallic ink on at least a portion of the        diffraction grating.

Furthermore, it would be advantageous to form the diffraction grating inregister directly on the substrate to which the holographic image is tobe applied.

In accordance with a further aspect of the present invention, there isprovided an apparatus for forming a security product comprising aprinting press and diffraction grating forming means.

The printing press may comprise any one or more of a

-   -   a) a feed system;    -   b) means to carry an image to be printed;    -   c) means to apply an ink to;    -   d) means to dry or cure the ink;    -   e) means to carry the printed security product.

The feed system may be a sheet or web feed system.

The means to carry an image may comprise a set of cylinders or a plate.In one embodiment, making use of GRAVURE printing, the means to carry animage comprises a plurality of cylinders, each of which carries anengraved image for each coloured ink used. Each cylinder or plate fordepositing/applying a colour is termed a print unit. There can be anynumber of print units. Preferably, however, there are between 1 and 10.

The means to carry the printed security product may comprise a deliverysystem for stacking sheets or holding finished reels.

The above methods may all comprise subsequently printing of the basematerial or substrate with pigmented inks. Alternatively, the methodsmay all comprise the pre-step of printing the base material or substratewith pigmented inks.

In one embodiment, the base material or substrate is paper.

In accordance with a further aspect of the present invention, there isprovided a method for forming a holographic diffraction grating on asubstrate comprising the steps of:

-   -   a) depositing on at least a portion of the substrate a        composition comprising a metallic ink admixed with a curable        compound;    -   b) forming a diffraction grating on at least a portion of the        composition.

In accordance with a further aspect of the present invention, there isprovided a method for forming a holographic diffraction gratingcomprising the steps of:

-   -   a) providing a sheet of base material;    -   b) depositing a release coating to at least a portion of the        base material;    -   c) depositing a curable compound on at least a portion of the        coated base material;    -   d) forming a diffraction grating on at least a portion of the        curable compound;    -   e) depositing a metallic ink on at least a portion of the        diffraction grating; and    -   f) depositing an adhesive on at least a portion of the metallic        ink.

The present invention provides methods of transferring a sub-microscopicimage or holographic diffraction grating and by means of printing anink, to form a composite sheet which when viewed from at least onesurface of the substrate or base material reveals the formedsub-microscopic or holographic diffraction grating patterns or images.

The finished pattern or image may be fully printed with the metallic inkor have degrees of ink density which allows a partial metallisationeffect of the image or pattern, whereby printing or text can be readilyviewed through the image when applied to a filmic or paper substrate,for use on security products such as identification documents likepassports, identification cards, drivers licenses, or other verificationdocuments, pharmaceutical apparel, software, compact discs, tobacco andother products prone to counterfeiting or forgery, to protect them fromfraudulent conversion, diversion i.e taking a product that should besold in one market and selling it in another, or imitation.

The sub-microscopic images, holographic or other diffraction gratingsmay be transferred to the surface of the substrate specifically inregistration or randomly for subsequent further registration ofadditional print units.

Once the image/pattern has been made visible by the overprinting of themetallic ink the image/pattern can not be again transferred to anothersurface other than by first depositing a release coat before forming thediffraction grating and hot stamped conventionally the substrate eitherfilmic or paper based.

The metallic ink provides a reflective background to the substrate.Preferably sufficient ink is deposited in one pass on conventionalnarrow or wide web printing presses, to provide the reflectivebackground. The printing press preferably comprises in line, anapparatus to transfer the sub-microscopic, holographic or otherdiffraction grating.

In-line is defined herein as printing in one pass, one operationimmediately after the next one on the same piece of machinery that isbolted together. Off-line is defined as a totally separate processcarried out on another piece of equipment.

In one embodiment the substrate is pre-printed. Pre-printing of thesubstrate may be carried-out separately, offline, on other dedicatedprinting equipment or in line on apparatus in accordance with thepresent invention.

An example of a metallic ink suitable for use in the methods andapparatus of the present invention is disclosed in co-pendingapplication filed by Wolstenholme International Ltd.

Preferably, the thickness of the metallic ink when deposited on asubstrate is sufficiently thin as to permit the transmission of lighttherethrough. Consequently, the metallic ink may be printed on thesubstrate over a sub-microscopic or holographic diffraction gratingpattern or image, such that the diffraction grating pattern or image maybe visible through both the upper and lower surface of the substrate.

Preferably, when the substrate carrying the metallised image or patternis subsequently over-laid onto printed pictures and/or text, or thesubstrate is pre-printed with pictures and/or text and the metallisedimage or pattern is deposited thereon those printed features are visiblethrough the substrate and/or the metallic ink coated diffraction gratingor image.

Preferably, the thickness of the metallised image or diffraction gratingis such as to provide an optical density in the range of lighttransmission. Optical densities of the layer of metallic ink can bemeasured by the Macbeth Densitometer set out in the following table:

Macbeth Optical Percent Density Units Transmission 0.10 79.43 0.20 63.100.30 50.12 0.40 39.81 0.50 31.61

Preferably, the percentage of light transmission is at least 30%. Morepreferably, the percentage of light transmission is at least 50%, mostpreferably, 80%.

The apparatus may comprise means to continually move the substrate, forexample a substrate feeder. The substrate may comprise any sheetmaterial. The substrate may be substantially transparent, translucent,or opaque. The substrate may comprise paper, filmic material or metal,such as aluminium. The substrate may be in the form of one or moresheets or a web.

The substrate may be cast, calendared, blown, extruded and/or biaxiallyextruded.

The substrate may comprise polymeric compounds. The substrate maycomprise any one or more selected from the group comprisingpolythyleneterephthalate, polypropylene propafilm, polyvinylchloride,rigid pvc, cellulose, tri-acetate, acetate polystyrene, polyethylene,nylon, acrylic and polytherimide board. The polythyleneterephthalatesubstrate may be Melenex type film orientated polypropylene (obtainablefrom DuPont Films Willimington Del. product ID Melinex HS-2)

The substrate may comprise papers made from wood pulp or cotton orsynthetic wood free fibres. The paper may be coated, calendared ormachine glazed.

The forming of a diffraction grating on the substrate may comprisedepositing a curable compound on at least a portion of the substrate.The lacquer may be deposited by means of gravure or flexographicprinting. The curable lacquer may be cured by ultraviolet (U.V.) lightor an electron beam. Preferably, the lacquer is UV cured. UV curinglacquers can be obtained from Kingfisher Ink Limited, (productultraviolet type UFV-203) or similar.

The U.V. light source may comprise a lamp. The lamp may have a power inthe range of 200-450 Watts.

Preferably, the U.V. lamp is disposed on or in the means for forming adiffraction grating.

In one embodiment, the transfer speed of the sub-microscopic holographicdiffraction grating image or pattern onto the surface of the printedlacquer will vary according to the power of the curing lamps.Preferably, the transfer speed is in the range of 10 metres to 20,000metres per hour, more preferably 18,000 metres per hour. Whilst incontact with the lacquer the sub-microscopic or holographic diffractiongrating is formed on the surface of the ultraviolet curable lacquerdisposed on the upper surface of the substrate.

The metallic ink may be applied to the substrate by means ofconventional printing press such as gravure, rotogravure, flexographic,lithographic, offset, letterpress intaglio and/or screen process, orother printing process. The substrate may then be rewound for subsequentoff line printing at a later stage or alternatively, the substrate maybe pre-printed in line or off line or subsequently printed in line.

The metal-based ink may comprise metal pigment particles and a binder.

The metal pigment particles may comprise any suitable metal. Theparticles may comprise any one or more selected from the groupcomprising aluminium, stainless steel, nichrome, gold, silver, platinumand copper. Preferably, the particles comprises metal flakes.

The metallic ink may be prepared by any means known to the skilled man.Preferably, a 12-micron thick transparent carrier film such asPolythyleneterephthalate obtained from DuPont Films Wilmington. Del.(Product ID Melinex HS-2) two metres wide is gravure coated with anacrylic resin isobutyl methacrylate obtained from DuPont (Product IDElvacite 2045) and dried by means of hot air. In a second operation theacrylic-coated film is deposition coated with aluminium by means of aroll to roll vacuum chamber. The deposition rate and thickness of thevaporised aluminium layer over the printed acrylic coating is accuratelycontrolled through continuous monitoring of the optical density duringmanufacture. The operating range of vacuum deposition may be in therange of 100 to 500 angstroms thick, the preferred thickness is in therange of 190 to 210 angstroms thick.

The optical density may in the range of 0.2 to 0.8 as measured on theMcBeth densitometer. Preferably, the range is 0.5 to 0.8. Morepreferably, the optical density is 0.7 as measured on the McBethdensitometer.

The metal layer may comprise aluminium, stainless steel, nichrome, gold,silver, platinum or any other metal which can be vaporised and depositedby vacuum deposition or applied by sputtering or electron beamdeposition. Preferably, the metal layer comprises aluminium.

The aluminium layer may be removed from the carrier film by means ofdesolving the acrylic supporting layer in a bath containing ethylacetate releasing the aluminium layer from the carrier film. Theresulting aluminium in the form of a coarse flake in the resin solutionmay then be washed in a multi stage centrifuging process to remove theacrylic resin. The coarse aluminium flakes are mixed with ethyl acetateand disintegrated by a high shear mixing process to produce a controlledparticle size distribution. The average particle diameter may be in therange of 8 to 15 microns the preferred range being 9 to 10 micronsdiameter as measured by a Coulter LS130 l.a.s.e.r. diffractiongranulometer.

In order that the sub-microscopic or holographic diffraction gratingpattern or image is clearly visible on both the first and second surfaceof a clear filmic substrate and the first surface of a paper substrate,preferably, the aluminium or other flakes are printed in such a way asto align themselves with the contours of the sub-microscopic,holographic or other diffraction grating pattern or image surface wavelength such that the flakes conform to and follow the contours of thediffraction grating.

To accomplish this alignment of flakes to the contours of thediffraction grating wave length i.e. the distance between peak and peakor trough and trough of the sub-microscopic contour. The specificallyformulated metallic ink preferably has a very low binder content, highpigment to binder ratio and very thin aluminium flake, preferably in therange of 9 to 10 microns, consistent to maintain good adhesion of theink to the surface to the sub-microscopic or holographic diffractionpattern or image.

The binder may comprise any one or more selected from the groupcomprising nitro cellulose, vinyl chloride, vinyl acetate copolymers,vinyl, acrylic, urethane, polythyleneterephthalate, terpene phenol,polyolefin, silicone, cellulose, polyamide, rosin ester resins. Thepreferred binder is 50% nitrocellulose (ID nitrocellulose DHL120/170 andnitrocellulose DLX30/50 supplied by Nobel Industries) 50% polyurethane(ID Neorez U335 supplied by Avecia). The solvents may be ester/alcoholblends and preferably normal propyl acetate and ethanol in a ratio of20:1 to 30:1.

The preferred pigment to binder ratio is by weight in the range of 1.5:1to 3.0:1, preferably 2.5:1. The metal pigment content of the ink may bethe range of 2% to 4% by weight, and preferably 3%.

The means for forming a diffraction grating may comprise a shim or aseamless roller. The shim or roller may he manufactured from anysuitable material, such as nickel or polyester.

Preferably, the nickel shims are produced via a nickel sulphamateelectro-plating process. The surface of a photoresist glass plateholding the sub-microscopic or holographic diffraction grating may bevacuum metallised or sprayed with pure silver. The plate may then beplaced in a nickel sulphamate solution and over a period of timemolecules of nickel are deposited on the surface of the silver-coatedphotoresist, resulting in a master copy. Subsequent copies may be usedin transferring the image for reproduction, or transferring toultraviolet polyester shims or to make a seamless roller.

Polyester shims may be made by coating polyester with an ultravioletcurable lacquer and contact copying the master image and curing thetransferred image by means of ultraviolet light.

Seamless cylinders may be made using a metallised transfer film with asub-microscopic or holographic diffraction grating pattern or imagethereon, which may be fixed and transferred to a cylinder coated with anadhesive. The metallised transfer film may glued to the roller via anip. The adhesive may then cured, preferably by heat. Once cured thetransfer film is removed leaving the metallised layer with thesub-microscopic or holographic diffraction pattern or image on surfaceof the cylinder i.e. the roller. This is repeated until the cylinder iscompletely covered. This cylinder then may be placed in a casting tubeand cast with silicone to make a mould. The sub-microscopic image may bemoulded to the inside surface of the silicone in contact with image.

Once the silicone is cured the mould is removed and placed in a secondcasting tube. A casting roller may then be placed in the mould and castwith a hard resin, preferably cured with heat. Once cured the roller canbe removed from the mould, where the image in the inside surface of thesilicone has transferred to the outside surface of the resin cylinderand is ready for use, to transfer the sub-microscopic or holographicdiffraction grating pattern or image on the surface of the cylinder intothe surface of a printed ultraviolet curable lacquer on the firstsurface of a substrate, and subsequently printed with the metallic ink.

In another embodiment a cylinder is coated with ultraviolet curableresin, placing a clear transfer film with a sub-microscopic orholographic diffraction pattern or image to the surface of theultraviolet resin via a nip and cured with ultraviolet light. Thecylinder can then be subsequently cast, as described above and used todirectly transfer the sub-microscopic or holographic diffraction patternor image into the surface of a printed ultraviolet cured lacquer on thefirst surface of a substrate. Alternatively, the substrate may besubsequently printed with metallic ink off-line on conventional printingequipment.

The upper surface of the substrate may be printed with a metallic ink indiscrete registered i.e. registered with other print already on thedocument etc., or in a position on the document etc., so that othersubsequent printing can take place and/or non-registered areas asimages/patterns, or in a stripe in discrete registered and/ornon-registered or all over the substrate surface. The substrate may thenpass through a nip roller to a cylinder carrying sub-microscopic,holographic or other diffraction grating pattern or image in the form ofa nickel or polyester shim affixed to the surface of a cylinder. In apreferred embodiment the images or patterns are held on a seamlesscylinder so that the accuracy of the transfer can be improved a cylinderwith the sub-microscopic pattern or image on it means. Thesub-microscopic diffraction or holographic grating may then betransferred from the shim or seamless roller into the surface of theexposed ultraviolet lacquer by means of bringing the surface of the shimor seamless roller into contact with the surface of the exposedultraviolet lacquer. An ultraviolet light source may be exposed throughthe upper surface of the filmic substrate and instantly cures thelacquer by exposure to ultraviolet light. The ultraviolet light sourcesmay be lamps in the range of 200 watts to 450 watts disposed inside thecylinder, curing through the printed ultraviolet lacquer and fixing thetransferred sub-microscopic or holographic diffraction grating.

Specific embodiments of the present invention will now be described, byway of example only, with reference to the accompanying examples andfigures, in which:

FIG. 1 is a schematic representation of a process for creating asub-microscopic, holographic or other diffraction grating in accordancewith the present invention using direct ultra violet curable lacquerover-printed with metallic ink;

FIG. 2 is a schematic representation of the process of FIG. 1 reversed;

FIG. 3 is a schematic representation of a process for creating asub-microscopic, holographic or other diffraction grating in accordancewith the present invention using a ultra violet curable metallic ink;

FIG. 4 is a schematic representation of the process of FIG. 3 reversed;

FIG. 5 is a schematic representation of a conventional printing processhaving an embossing station added in-line;

FIG. 6 is a schematic representation of a conventional printing processhaving an embossing station added in-line;

FIG. 7 is a perspective view of a schematic representation as shown inFIGS. 3, 4 and 6;

FIG. 8 is a perspective view of a schematic representation of a processfor forming a sub-microscopic, holographic or other diffraction gratingin a substrate in accordance with the present invention in register;

FIG. 9 is a perspective view of a schematic representation of a processfor forming a sub-microscopic, holographic or other diffraction gratingusing a crating? an a non-embossable substrate;

FIG. 10 is a perspective view of a schematic representation using forforming a diffraction grating on a non-embossable substrate in register;

FIG. 11 is a perspective view of a schematic representation of a processfor forming a diffraction grating not in register;

FIG. 12 is a cross-sectional schematic view of one embodiment inaccordance with the present invention;

FIG. 13 is a cross-sectional schematic view of one embodiment inaccordance with the present invention;

EXAMPLE 1 Direct Ultra Violet Curable Holographic Print Over-Printedwith Specially Formulated Metallic Ink (Film)

Referring to FIG. 1., a filmic substrate such as OPP or PET, (1) isprinted with an ultra violet curable lacquer (2) on its upper surface. Aholographic diffraction grating is cast (3) into the surface of thelacquer (2) with a nickel shim (4) having the holographic gratingthereon. The holographic image in the form of a diffraction grating isimparted into the lacquer and instantly cured (5) via a U.V. lampdisposed in shim (4) at normal processing speeds. The holographic imageis a facsimile of the grating. Metallic ink (6) is printed (7) over theholographic grating and causes the holographic diffraction grating tobecome light reflective, the diffraction grating is visible on bothsides of the filmic substrate. Further colours (8) can be subsequentlyconventionally printed in-line at normal printing process speeds.

In an alternative embodiment, the filmic substrate (1) is replaced withpaper/board substrate. Such material is substantially opaque andtherefore the holographic image is only visible when viewed from theupper surface.

EXAMPLE 2 Reverse of Example 1 Above (Film)

As shown in FIG. 2, Filmic substrate (1) is printed conventionally witha number of coloured inks. Using, for example, a Cerutti R950 printer(available from Cerrutti UK Long Hanborough Oxon.) (8), substrate (i) isthen printed with an ultra violet curable lacquer (2) on the surface ofa filmic substrate (1). A holographic diffraction grating is cast (3)into the surface of the lacquer (2) with a nickel shim (4) having theholographic grating thereon, the holographic image is imparted into thelacquer and instantly cured (5) via a UV lamp (not shown), becoming afacsimile of the grating disposed on the shim. A metallic ink (6) isprinted (7) over the holographic grating and causes the holographicdiffraction grating to become light reflective, the diffraction gratingis visible on both sides of the filmic substrate.

In an alternative embodiment, the filmic substrate (1) is replaced withpaper/board substrate. Such material is substantially opaque andtherefore the image is only visible when viewed from the upper surface.

In another embodiment, the UV curable lacquer is replaced with anelectronic beam curable lacquer and the UV lamp replaced with anelectron beam emitting device.

EXAMPLE 3 Direct UV (Ultra Violet Curable Ink)

Referring to FIG. 3, a UV curable variant of the metallic ink is printedon substrate (1) in and/or out of register using standard printing andcoating equipment including Rotogravure/Flexographic methods into anycompatible substrate surface. The embossing shim, dye or cylinder isbrought into direct contact with the metallised ink (2). Whilst in aliquid state the ink is flash cured virtually instantaneously using a UVlight source (3), through the substrate whilst the embossing shim, dyeor cylinder remains in direct contact with the metallic ink using a UVtype embossing machine. The surface tension of the substrate beinggreater than that of the embossing shim, dye or cylinder causes the inkto adhere to the substrate rather than the embossing shim, in a curedstate, replicating and retaining the surface relief characteristics,integrity, holographic, diffractive or other sub-microscopic structureor micro-texture properties and effects within the metallised ink whichis now incorporated onto the surface of the substrate.

EXAMPLE 4 Reverse of Example 3 Above

FIG. 4 shows the use of a UV curable variant of the metallic ink a UVtype embossing engine is used. The ink is printed (1) in or out ofregister using standard printing and coating equipment includingRotogravure/Flexographic methods into any compatible substrate surface.The embossing shim, dye or cylinder is brought into direct contact withthe metallised ink (2). Whilst in a liquid state the ink is flash(virtually instantaneously) cured using a UV light source (3), throughthe substrate whilst the embossing shim, dye or cylinder remains indirect contact with the metallic ink. The surface tension of thesubstrate being greater than that of the embossing shim, dye or cylindercauses the ink to adhere to the substrate rather than the embossingshim, in a cured state, replicating and retaining the surface reliefcharacteristics, integrity, holographic, diffractive or othersub-microscopic structure or micro-texture properties and effects withinthe metallised ink which is now incorporated onto the surface of thesubstrate.

EXAMPLE 5 In-Line Printing

FIG. 5 shows that a conventional printing press Rotogravure, UVFlexographic or similar can have an extra station added, this being anembossing station (1) either Hard, when a pre-metallised material isembossed between a steel cylinder and tough but compliant roller. Softwhen a material embossed with a steel cylinder and soft compliant rollerthen subsequently metallised UV or electron beam cured). Using anyembossable film (2) either native/raw film/substrate such as Co-extrudedBOPPs, Polyolefin's, Polyesters and Cellulose or pre-coated/lacquered.The substrate is first embossed (first station) (1) then printed (secondstation) (3) using a specifically formulated metallic ink to produce themetallised effect. Conventional printing (4) can also be carried out onthe same press. As the ink is formulated like a normal ink, conventionalprinting methods can be utilised. The printing of the metallic ink canbe anywhere in the line; it does not have to come directly afterembossing. If an encoder for example an indexing machine which marks thesheet or web so that the mark can be recognised by the print operator(5) is placed in the embossing area and the embossing head has specifiedareas of imagery, then register to print can be achieved. Printing ofthe metallic ink can be solid, semi translucent etc, with the resultingeffect being that in one pass of the printing press metallising,semi-metallising, de-metallising and normal printing of colours in ornot in register can be achieved. The specifically formulated metallicink can be printed on either side of the film, however generally thiswill be carried out on the embossed side, to encapsulate the holographicembossed image/pattern so that it remains intact, should it come intocontact with any filling agents such as liquids, grease, solvents,lacquers, inks or any other surface contaminants or foreign bodies ofany kind.

EXAMPLE 6 Dual In-Line Printing

A conventional printing press Rotogravure, UV Flexographic etc. can havean extra station added, this being an embossing station, either Hard,Soft electron beam or UV. Utilising an existing or adding an additionalprint station (2), a holographic embossable substantially transparentcoating can be printed coated laid down (This coating/lacquer generallybeing Nitro-Cellulose based, solvent evaporated), either on the wholesurface of the substrate, partially or printed in register (for laterre-registration by subsequent embossing and or print/coating stations).This area is then ready to be embossed and eliminates the need forpre-coated/lacquered films/substrates.

FIG. 6 shows a substrate first coated/lacquered (first station) (2) thenembossed (second station) (1) and then using a third conventional (3)Rotogravure/Flexographic print station, to print the speciallyformulated metallised ink, producing the reflective silver metallisedeffect, is printed on the embossed side of the substrate/film. Thenprinting of other inks can be carried out as normal (4). The speciallyformulated metallised ink can be printed on either side of the film,however generally this will be carried out on the embossed side, toencapsulated the holographic embossed image/pattern so that it remainsintact, should it come into contact with any filling agents such asliquids, grease, solvents, lacquers, inks or any other surfacecontaminants such as liquids, grease, solvents, lacquers, inks or anyother surface contaminants or foreign bodies of any kind.

EXAMPLE 7 Transfer

FIG. 7 is a film that has a release coat, either applied/coated in-lineor is part of the film's/substrate's design/construction intentionallyor not is embossed (as in FIGS. 5/6/8), and then printed with themetallic ink, either in register of not (1), and then an adhesive (2) isapplied again either all over or in register with the embossed image,then laminated to various substrates, (paper, Board, film) (3)/Once theadhesive is cured either in/on or off line the film can then be stripped(4) leaving the embossed and metallic area on the substrate (5), thistransferred area can subsequently be over printed, providing either acompatible ink is used or a print receptive coating is applied to assistink key, again this can be produced in, on or off-line.

EXAMPLE 8 Off-Line (in Register) Printing

FIG. 8 is a schematic of a method to emboss a substrate using either aHard, Soft electron beam or UV embosser. This is done by passing asubstrate (1) through an embossing cylinder (2) and a nip roller (3),the embossing cylinder (2) has an embossing shim made of metal orplastic or directly on the cylinder (4) with a holographic/diffractiveor engraved image (5) and with heat and pressure or UV curing embossimage (6) into various substrates. If a registration mark (7) is on theembossing cylinder this will also emboss on to the substrate (8). Thesubstrate is then printed using specially formulated metallic ink on aconventional printing press. The specially formulated metallic ink canbe printed down as a solid to give a full metallised effect or differentcoat weights to give different types of effects i.e., a semi metallised(HRI effect) etc. The substrate can be printed all over or because aregistration mark (8) has been embossed on the substrate the speciallyformulated metallic ink can be printed in specified areas in registerwith the embossed image and normal printed images. If a transfersubstrate is embossed then after printing of the formulated metal inkthe substrate can be used for ‘Transfer-metallising’ on to paper, board,film and metal foils.

EXAMPLE 9 Emboss in Register

Registering a holographic/diffractive embossed area/image to print andor lacquered area or vice versa can be performed using two methods.

1. Utilising the Standard Native Embossable Films/Substrates.

The film can be either embossed in register and subsequentlyprinted/over printed, or pre-printed and subsequently embossed inregister to the printed areas in-line, on-line or off line, by means ofregistering and adjusting electronically the embossing cylinder to thesubsequent printing cylinder or vice versa, or by means of aholographically, chemically, etched or engraved registration markincorporated on the embossing shim/cylinder, this will then produce awhite/grey registration mark when embossed into the film. For subsequentregistration by electronically controlled photo cell either reflectiveor transmissive and printing in a specified area/areas, thus enablingthe embossing station to be positioned anywhere in the machine systemconfiguration, previous to the metallic ink printing that will be usedas the reflective background to the holographic/diffractive embossedareas.

2. Utilising Lacquers/Coatings on Non-Embossable Films/Substrates.

-   I. To facilitate the use of a clear/transparent embossable    coating/lacquer on normally un-embossable films/substrates for    subsequent embossing and printing. A clear/transparent embossable    coating/lacquer is printed over the entire surface of the    film/substrate for subsequent embossing and/or printing. (see FIG.    9).-   II. (FIG. 10) To allow the use of a clear/transparent embossable    coating/lacquer on normally un-embossable films/substrates for    subsequent embossing and printing. IN REGISTER. The use of an ink    jet printer/encoder is incorporated on the print station (1) that    will be used for the printing of an embossable coating/lacquer, once    the embossable coating/lacquer area has been printed (2), the ink    jet printer/encoder will register to a registration mark (3), notch,    space etc. that is incorporated on the printing    cylinder/sleeve/plate (4), once triggered by the electronic photo    cell that detects the registration mark, the ink jet printer (5) is    electronically/computer controlled to print a registration mark (6)    on the film/substrate for later registration and embossing (7) into    the embossable lacquer/coated areas (2), and for subsequent    registration by further print stations (8) down line.

EXAMPLE 10 Off-Line (Not in Register) Printing

FIG. 11 shows a schematic of a method to emboss a substrate using eithera Hard, Soft or UV embosser. This is done by Passing a substrate (1)through an embossing cylinder (2) and a nip roller (3), the embossingcylinder (2) has an embossing shim made of metal or plastic or directlyon the cylinder (4) with a holographic/diffractive or engraved image (5)and with heat and pressure or UV curing emboss image (6) into varioussubstrates. The substrate is then printed using specially formulatedmetallic ink on a conventional printing press. The ink can be printeddown as a solid to give a full metallised effect or different coatweights to give different types of effects i.e., a semi metallised (HRIeffect) etc. The substrate can be printed all over or because aregistration mark (8) has been embossed on the substrate the speciallyformulated metallic ink can be printed in specified areas in registerwith the embossed image and normal printed images. If a transfersubstrate is embossed then after printing of the formulated metal inkthe substrate can be used for ‘Transfer-metallising’ on to paper, board,film and metal foils.

Referring to FIG. 12 a film substrate 100, UV curable lacquer 102 andholographic or other sub-microscopic diffraction grating 104 withmetallic ink 106 printed over with both first 108 and second surfaces110 viewable.

Referring to FIG. 13 a paper substrate 120, UV curable lacquer 122 andholographic or other sub-microscopic diffraction grating 124 withmetallic ink 126 printed over with the image viewable through the firstsurface 128 only.

1.-52. (canceled)
 53. A method for forming a security product comprisingthe steps of: a) providing a sheet of base material, said sheet havingan upper and lower surface and being a component of the securityproduct; b) forming a diffraction grating on at least a portion of theupper surface of the base material; and c) depositing a metallic ink onat least a portion of the base material.
 54. The method of claim 53,wherein the thickness of the metallic ink when deposited on a substrateis sufficiently thin as to permit the transmission of lighttherethrough.
 55. The method of claim 54, wherein the percentage oflight transmission is at least 30%.
 56. The method of claim 55, whereinthe optical density of metallic ink when deposited is in the range oflight transmission.
 57. The method of claim 56, wherein the opticaldensity is in the range of 0.2 to 0.8 as measured by a Macbethdensitometer.
 58. The method of claim 53, wherein the metallic inkcomprises metal pigment particles and a binder.
 59. The method of claim58, wherein the pigment particles comprise any one or more selected fromthe group consisting of aluminium, stainless steel, nichrome, gold,silver, platinum and copper.
 60. The method of claim 58, wherein thethickness of pigment particles is in the range 100 to 500 angstroms. 61.The method of claim 58, wherein the thickness of pigment particles is inthe range of 190 to 210 angstroms.
 62. The method of claim 58, whereinthe thickness of pigment particles is in the range of 100 to 210angstroms.
 63. A hologram obtained using the method of claim
 53. 64. Anin-line method of printing on a substrate using a conventional printingpress apparatus together with means for forming a diffraction grating,comprising the steps of: a) forming a diffraction grating on a discreteportion of the substrate; and b) depositing a metallic ink on at least aportion of the diffraction grating.
 65. The method of claim 64, whereinthe step of forming of a diffraction grating on a substrate may comprisedepositing a curable composition on at least a portion of the substrate.66. The method of claim 64, wherein the curable composition is alacquer.
 67. The method of claim 66, wherein the curable lacquer iscured by means of an ultraviolet (U.V.) light or an electron beam. 68.The method of claim 65, wherein the diffraction grating is formed on thesurface of the curable composition as it is disposed on the substrate.69. The method of claim 64, wherein the thickness of the metallic inkwhen deposited on a substrate is sufficiently thin as to permit thetransmission of light therethrough.
 70. The method of claim 64, whereinthe metallic ink comprises metal pigment particles and a binder.
 71. Themethod of claim 70, wherein the thickness of pigment particles is in therange 100 to 500 angstroms.
 72. The method of claim 70, wherein thethickness of pigment particles is in the range of 190 to 210 angstroms.73. The method of claim 70, wherein the thickness of pigment particlesis in the range of 100 to 210 angstroms.
 74. A method for forming aholographic diffraction grating on a substrate comprising the steps of:a) depositing on at least a portion of the substrate a compositioncomprising a metallic ink admixed with a curable compound; b) forming adiffraction grating on at least a portion of the composition.
 75. Themethod of claim 74, wherein the metallic ink comprises metal pigmentparticles and a binder.
 76. The method of claim 75, wherein thethickness of pigment particles is in the range of 100 to 210 angstroms.77. A method for forming a holographic diffraction grating comprisingthe steps of: a) providing a sheet of base material; b) depositing arelease coating to at least a portion of the base material; c)depositing a curable compound on at least a portion of the coated basematerial; d) forming a diffraction grating on at least a portion of thecurable compound; e) depositing a metallic ink on at least a portion ofthe diffraction grating; and f) depositing an adhesive on at least aportion of the metallic ink.
 78. The method of claim 77, wherein themetallic ink comprises metal pigment particles and a binder.
 79. Themethod of claim 78, wherein the thickness of pigment particles is in therange of 100 to 210 angstroms.